Pythagorean Theorem Calculator
Free Pythagorean theorem calculator: find the missing side of a right triangle from the other two, with the area, perimeter, angles and height.
What it does
In a right triangle the square of the hypotenuse (the side opposite the right angle) equals the sum of the squares of the other two sides, the legs: a² + b² = c². This calculator finds the missing side from the other two and also gives the area, perimeter, the two acute angles and the height to the hypotenuse.
How to use it
- Type the two sides you know.
- Leave the side you want to find empty.
- See the missing side, the area, the perimeter and the angles.
The arithmetic runs in your browser. Nothing you type is sent anywhere and nothing is stored, so you can use these with real numbers.
Frequently asked questions
How do I find a leg instead of the hypotenuse?
Subtract instead of adding: a = √(c² − b²). With a hypotenuse of 5 and a leg of 4, the other leg is √(25 − 16) = 3.
What are Pythagorean triples?
Whole numbers that fit a² + b² = c², such as 3-4-5, 5-12-13 and 8-15-17. Builders use 3-4-5 to check that a corner is square.
Does it work for any triangle?
Only for right triangles. For other triangles use the law of cosines, c² = a² + b² − 2ab·cos C, which the triangle calculator applies.
Do the units matter?
Use the same unit for all sides; the missing side comes out in that unit and the area in square units, for example cm and cm².
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